High growth rate MOVPE of Al(Ga)N in planetary reactor

摘要

Possibility of A1N growth by MOVPE in a planetary reactor with high growth rate was investigated. Growth was performed on (0001) Al_2O_3 substrates at the reactor pressure of 100 mbar. It was shown that deposition rate is close to diffusion limit at low NH_3 flows and reduces abruptly above a certain threshold value of NH_3 due to gas-phase parasitic reactions. At constant V/III ratio of 1.5-2, A1N growth rate dependence on TMAI flow was linear and a maximum growth rate of 8.6 μm/h was achieved. Process modeling allowed predicting and explaining the trends related to the onset of parasitic chemistry for various V/III ratios and other growth conditions. Surface morphology penalization was achieved by either (1) NH_3 flow rate reduction or (2) TMGa injection after the layer with thickness of 75-300 nm was grown. The second approach looks more fruitful resulting in atomically flat Al(Ga)N layers with a 2 μm/h growth rate. For the conditions (high temperature, low NH3 and high H_2 concentration) used Ga acts mostly as surfactant (Ga content in Al(Ga)N is about 3-5%).